Normalizing device for gear train shutter retards



March 11, 1952 H. T. HODGES 2,588,980

NORMALIZING DEVICE FOR GEAR TRAIN SHUTTER RETARDS Filed April 22, 1950 2 SHEETSSHEET l HOWARD T. HODGES I N VEN TOR ATTORNEYS March 11, 1952 H. T. HODGES 2,538,980

NORMAL-IZING DEVICE FOR GEAR TRAIN SHUTTER RETARDS 2 SHEETS--SHEET 2 Filed April 22, 1950 HOWARD T. HODGES I) N VEN TOR MzKM TRA VEL OF STAR WHEEL SECTOR PIN TEETH TRAVEL O00 TIM/N OUT PALLET 026 our 44 050 I 0/8 PALLET \SHU TTER SPEED /4ao V200 7100 Z50 ATTORNEYS Patented Mar. 11, 1952 N ORMALIZIN G DEVICE FOR GEAR TRAIN SHUTTER RETARDS Howard T. Hodges, Rochester, N. Y., assignor to Eastman Kodak Company, Rochester, N. Y., a corporation of New Jersey Application April 22, 1950, Serial No. 157,580

8 Claims.

This invention relates to photography and more particularly to a means for obtaining accurate retarding from a shutter employing a gear train retard. One object of my invention is to provide a shutter retard in which a weighted member will always have a predetermined position of rest. Another object of my invention is to provide a retard mechanism in which there is a means for overcomin the effects of play between teeth in gears of a gear retard. Still a further. object of my invention is to provide a means by which the fastest moving part of the gear train, which is usually a weighted member, may be held in a fixed relation with respect to the slowest moving part of the gear train which is usually a gear segment. Still another object of my invention is to provide a gear retard with a meansfor holding the gear segment in an operative position and in contact with a speed-control cam, and to also provide the fastest moving part of the gear train with a means for holding it in a predetermined relation with respect to the gear segment; A still further object of my invention is to provide a magnetic device for materially increasing the efficiency of a gear retard mechanism for shutters. Other objects will appear from the following specification, the novel features being particularly pointed out in the claims at the end thereof.

The problem of obtaining accurate and consistent speeds upon successive operations of any shutter is a diflicult one. Many shutters when successively tripped do not produce accurate speeds consistently, nor do they produce the same speeds consistently, whether accurate or not. The simplest type of shutter to time in assembling the shutter is one in which a simple weight can be held in a predetermined position by a spring from which position it may be moved by the shutter mechanism. Such retards, of course, are only employe'd for shutters having very few speeds. They" are, however, frequently quite consistent. The more shutter speeds which are provided for, the more the difiiculty in maintaining these speeds accurate and in timing the speeds to a reasonable tolerance. During the War, a war emergency standards for photographic shutters was set up. This provided the efiective fullopening period of shutter blades should be within plus or minus 20% for /moth of a second or slower, and within plus or minus 30% for exposures faster than moth of a second when the shutter is operating in temperatures of from 32 to 104 F. Thus, the difliculty of timing shutters is recognized by this standard which will probably be followed by American standards. The reason a simple weight is very effective as a retard for one, or perhaps two speeds is, of course, that the weight may always be held in the same position so that when the driving member comes along it will engage the weight under standardized conditions. With the more expensive shutters, a weight is still used as a part of a retarding mechanism, but in order to produce more retarding effects, usually two or more gears conmet the weight with the gear segment which is the member against which the shutter-operating mechanism moves each time a retarded mechanism is set so that the gear segment may move the gears and the weight. In many shutters the weight may be in the form of a starwheel, but, in any event, the fastest moving part of the gear train is usually spaced from the gear segment by a number of gears. Unfortunately, perfect gears are not available at any price, so that a perfect gear train for shutters does not exist. In the better gear trains, of course, where the teeth are out, there may be very little play between the teeth but very little play is suflicient to prevent repeated actuations of a shutter at one shutter speed setting at speeds which are consistent and close to the desired speed.

One of the difficulties with gear train retards is that when the shutter is set the gears are turned in one direction and the weighted member turns faster than the other gears and, consequently, the speed of setting a shutter may affect the gear train because if it is set slowly,

the weighted member will probably rebound less than if the shutter is set quickly. In other words, the weight tends to turn after movement of the gear sector setting it is actually stopped and, therefore, if there is any play in the gears this play may lie in almost any direction according to the various forces involved. With such conditions, it is impossible to obtain speeds which are close to the rated speed and speeds which can be repeated at will without varying in a plus or 'minus direction from the rated speed.

I have largely overcome this difilculty by providing a gear train with a magnetic means for holding the weighted member in a preferred position of rest, particularly for a certain speed, or speeds. This preferred position is in some re spects unimportant, so lon as it is a consistent position, because the gear train will then always afford the same resistance under the same circumstances, particularly as the gear sector at the opposite end of the train is always held by its own spring against a timing cam so that it, too.

amount. However, by normalizing the position of the weighted member, most of the difliculties which have heretofore occurred can readily be ironed out and unusual uniformity can be obtained.

Coming now to the drawings wherein like ref erence characters denote like parts throughout:

Fig. 1 is a fragmentary front view with parts broken away showing a known type of shutter" equipped with a retard constructed in accordance with and embodying a preferred form of-my invention; I V

Fig. 2 is a perspective view of the permanent magnet and polarized element as included in the retard'shown in Fig. 1; I V r Fig: 3-is a fragmentary side elevationwith partsbeing shown in section of the retard shown Fig.4 is a fragmentary," somewhat schematic,

Fig. -6 is'a chart of a typical high-grade shutter showing the various speeds operating without a gearftrainythe speeds operating with the gear' train,- but without the'palletyancl the speeds operating with the gear train withthe pallet in. This-chart shows the travel in teeth of the starwheel for the various types of" exposures;

,AS 'a typical" example "of *a shutter whichcan be advantageouslyequipped with-a gear train constructed in accordance with -my invention,

reference'may be had to U. S. application Serial- No;728, 528; 'Direct Acting Shutter for Cameras, filed February '14, 1947, by Carl C. Fuerstand-resulting in Ups Patent No. 2,524,786, granted October-;10, 1950.

In the drawing 10f this case, 'Fig. 1 shows, somewhat schematically, the partscorresponding to the shutterin the above application consisting of-a-shutter casing-I having an--upstandin g As will be pointed out herein-.

flange 2- around the periphery and-a central "exposure aperture'3. A mechanism plate-'4 may" support parts; of the shutter blade driving mechanism; the shuttergblades- 5 being pivotally mounted" at 6,-Fig.' 5, to the shutter casing and being movable about these pivots-yby pivot 1 from the position shown in-Fig. -1 wherein'the shutter is shown as being set. In thisset posi tion, the blade ring 8 and its operating or settin handled!) have been moved to a set position in which a latchelement ll may be held against movement by 'a latch element pressed in thedirection shown by the arrow by means of a spring l4 until a lug'l5 engages an-edge of a release lever It also" pivoted upon the stud l3.

This release" lever has a cam end I! which engages a driving cam l8 on a power-operated meta--= l2 pivotally mounted on a'stud'l3. -This latch-element is a 4 her l9. his member is mounted to turn upon a stud 20 when the shutter parts are in the set position shown, since the interengaging cams l1 and I8 are in substantial alignment between the pivotal points I3 and 20, the power-driven memher [9 is held against movement. However, when a'trigger 2 l is moved in the direction shown by the arrow in Fig. 1, a lug 22 engages trip lever l6 and moves it a short distance toward the center of the shutter.

After such movement, the power-operated member takes over and continues to move the trip'leve'r I6 until the latch l2 releases the latch element 1!. A driving spring 23 attached to "flange '2 at 24 and attached to the blade ring 8 at 25 will then drive the blade ring in a counterclockwise direction causing the shutter leaves 5 to open and close and thereby make an exposure. As indicated in the above-mentioned application, the trigger likewise operates a pair of cover blades to close the exposure aperture while the shutter is being'set,but, since this'forms no part of the present application, this structure need "not be described herein.

In setting the shutter by the handle It, the blade ring '8 moves a pin 26 so that it connects with'oneend 2'! of a bell crank lever pivoted on the stud and having a second arm 28 extending" upwardly through an arcuateslot 29 the There is a light spring" 30 encirclingthe stud 20' having one end resting onthe case and the other 'end 'lying directlybeneath'the'arm of spring 3! lying against 'the" lug 28. This spring tends to turn member-I9 in" the bell crank in a clockwise direction when lu Thus, the function is that'with the'bell crank arm 21 held set as in Figml, a spring 35 exertsa torque'ona pin 36 which will overcomespririgBiJ assoon ascam 11 is moved a sufficient distance by trigger 2| to-releasecaml8, enabling thepower-drive'n power-driven member.

28 contacts with the end of slot 29.

memberlQ to continue the releasing'movement of thelatch element l6 until the shutter is reoperating mechanism where in a gear retard is used, and wherein the gear'retard is moved across a path followed by a pin on the shutter operating mechanism which moves withthe shutter leaves to retard the shutter leaf movement. I

Byclosely studying the retarding action ofa v number of shutters, it has been determined that" ni h th m w ll f i e t w h a be cut, all of the gear trainswill have slight play he; tween the teeth and, consequently, when the gear j sector :orgear driving memberis positioned in a predetermined position, the fastest moving gear of the gear train may not-be in a predetermined position, and this is also true of the intermedi-.

ate gears. If this gear play can be satisfactorily Hair taken up. improved results" would occur. springs have been tried for this purpose butthe difficulty with such a spring is that withinthef limits of a shutter it is not practical to use such a spring on the fastest moving gear, particularly where such a gear may have to revolve three or four-times because there is no room for the;

Such

longspring which would be required. springs applied to intermediate gears have improved the operation of gear trains but'they have not by any means corrected-the difiiculties 'with -'them: Y

ReIerring to the chart in Fig. 6, wherein is charted the various speeds of a typical high-grade shutter, column A shOWS the various shutter speeds from th of a second to one second. Column B shows the travel of the sector pin, this sector pin being pin 50 and being selected because it was comparatively simple to measure the movement of this pin. Column C designates the starwheel travel; this travel being measured by teeth on the starwheel. In the present instance, the gear train had a 20-tooth starwheel so that, as will be noticed from this chart, only the 200th of a second indicated in line D, the 10th of a second and 5th of a second in lines E and F, required less than a single revolution of this starwheel and its gear. Therefore, with this particular shutter the difficult speeds to time acv curately are the 200th, the th, and 5th.

Y found that with the sector travel of .001, the

starwheel will move a distance of one-half a tooth. Therefore, if there is a one or two tooth movement due to lost motion, it is obvious that it is impossible to accurately time the shutter and to accurately repeat set speeds.

In order to overcome this difiiculty I have applied.a polarized member 5| to a starwheel 52 t which is the fastest moving gearof the gear train. The starwheel carries a pinion 53 meshing with a gear 54. In the present gear train there are a series of gears. Gear 54 turns with a pinion 55 meshing with a gear 56. Gear 56 carries a pinion 51 meshing with the teeth 58 of the gear segment 59 which I have called a gear sector which turns upon its shaft 60 and which includes an arm 6| lying in the path of pin movable with the master member 8. A spring 6| tends to turn the gear sector in the direction shown by the arrow and until the pin 50 contacts with a cam step 62, 63, 64, 65, or the like, carried by the ring 61 which is turned until a pointer 68 indicates on a scale 69 the setting of the shutter.

Ring 61 also carries a cam 80 contacting with a lug 8|, on bell-crank lever 82, pivoted at 83 to the shutter. Lever 82 pivotally supports at 84 a pallet-85 having arms 86 to engage the teeth of starwheel-52. When cam 80, Fig. 5, engages bell-crank lever 82, the pallet lies out of contact with the starwheel 52, but when cam 81 engages bell crank 82, a spring (not shown) moves the pallet 85 into engagement with the starwheel 52.

The polarized member 5| is shown as having a north and south pole-and I prefer to provide a small notch 10 in this member at right angles to the direction of polarization to assist in orienting this piece. A permanent magnet 12 is attached to an upper gear plate 13 as by a rivet I4 and adjacent the path of the polarized member, so that when the south pole of the polarized member 5| is oiTset at an angle from the polarized member 12, it will turn the starwheel 52 and with it the remaining gears of the gear train in order to take up or put in lost motion, according tothe position of the parts.

vAs pointed out above, the most difiicult speed to time is the /2outh of a second, because in this speed, as indicated in Fig. 4, the driving pin 25 6 barely touches the arm 6| of the gear sector 59 and moves it only a very slight distance. This distance with the particular shutter measured being .028" as indicated.

Consequently, the retarding action of the gear train must be free from play in one direction so that as the assembler times the shutter it may be properly timed. With the particular gear train mentioned, the total travel of the sector pin may be .028", while the total travel of the starwheel in teeth may be 14 teeth. Thus, the sensitivity for a plus or minus 20% change in speed would be .005" or 2.5 tooth travel of the starwheel. With variation in the position of the gears it is obviously dimcult or impossible to keep within a 20% change plus or minus. However, by orienting the polarized member 5| with respect to the magnet 12, when the gear train is set for /znoth of a second, all of the play may be eliminated in the gear teeth and the travel of the gear sector 59 will always be opposed in exactly the same manner by all the gears and, consequently, accurate exposures can be obtained.

Such orientation of the gears of the gear train make it possible to produce uniform exposures throughout the entire range of exposures of the shutter, because with the pallet out it will be noticed from Fig. 6 that only the 200th of a second turns less than a single turn.

For each revolution of the starwheel 52 there is a plus and minus torque between the polarized member 5| and the permanent magnet 12. Nev ertheless, this action is always the same so that for each total revolution it does not appear to affect the accuracy of the speed. Of course, with a speed such as a 25th of a second in which '70 teeth of the starwheel turn past a given point, there is little or no difiiculty in obtaining a perfectly accurate exposure.

When the pallet is put in, as shown by lines E and F, the starwheel travel is 9 teeth or 12% teeth for a tenth and a fifth of a second. Consequently, the orientation should also be such as to tend to turn the gears i one direction for these speeds. The assembler can readily take care of the orientation of the polarized member by Watching the notch 10. If it should be accurately aligned with the aXis of the permanent magnet 12, this orientation can be altered by lifting the gear sector 59 so that the gears of the segment 58 will disengage the pinion T0, enabling the gear train to be turned until the orientation of the polarized element 5| and the magnet 12 is oifset, and reengaging the sector 59.

Curiously enough, I have found in assembling a large number of polarized elements and magnets to shutters that it is scarcely ever necessary to orient the polarized element and magnet. By merely dropping them into place and testing the speed of the shutter, it would appear that if improperly oriented the play in the gear teeth might not be either taken out or put in. However, if the orientation is improper, it would immediately show up when the shutter assembler tried to speed the shutter as by filing or peening the speed cams. If the shutter would not repeat the shutter speed for which it is adjusted within very close tolerances, the shutter assembler would then change the orientation of the polarized element 5| and the magnet 12 which, as above explained, can be simply accomplished.

It is obvious that where the relationship of all the gears of a gear train is definitely established for any definite speed setting of the shutter, the travel of the arm 6| will always be the same. I

as se so have a'ceoniplished this by turning -the starwheel {by the -magnetic system abovedescrib'edand I have-been able in practice to take discardedshutters having one or more exposures whichcould not be accurately tim'ed andcould' not beadjusted to repeata predeterminedexposure and by applying my pol'a'ri'zed' element to the fastest moving gearof the train and the ermanent magnet 3 close-to the path of said memberg I 'have' been able to satisfactorily time such'shutters.

5 My device requires extremely 'little power beof the starwheel); Ihave, nevertheless; been able toobtain completely satisfactory results in putting'in all-of the' play betweenthe gear-teeth; rather '"than taking it out. Thus, actually, the gear-segment would start moving-before 'the star- Whel where play is'put into the-teeth, butjnevertheless, since-'the g'eartr'ain elements are-all "in' the same positionfor each speed setting-this 'doe's not afiect constantand accurate operation of the shutter if the shutter has been timed for this type-of control. All that is required is'that all the gea'r train gears or elements are in an exact predetermined position for each 'setting befo're an exposure is made.

While I have shown a preferrede'mbodime'ntof my invention applied to a camera shutter having a long range of exposures, it is 'obviouslyl'essdifficult to obtain' accurate speeds fromshutters having a 'shorter range of exposure. However, the aboveembodirnent illustrates a preferred and I entirely satisfactory form 'ofmy invention. 1 1 consider as within'the scope of thy-invention all such claims-as may-come within the scope-'of 'the appended claims.

* Having thus describedmy invention, what I "'cl'aim -is new and desire to secure by Letters Patent of the United States is:

' 13A normalizing device for camera: shut ters of the type including a shutter casing, an exposure aperture therein, shutter leaves pivotally mounted in the shutter'and-normally covering the'exposure aperture;- a power-drivenma'ster member 'opeia'bly connected to theshutter bla'des'for mov- -ingjthe' blades -to open and 'close'the exposure aperture, alatch for the master member, a latchreleasing mechanism'including a trigger, a retard 1 comprising a train of gears one'of which is a contact sector adapted to be=driven by the master member to' control the speed of operation thereof, means to control the shutter speed by moving the contact sector-relative to the master member, said retard normalizing device comprising a polarized member carried by a' member of the gear train spaced from the contact sector and a Dermanent' magnet adjacent thereto whereby-said magnet may tend to maintain'the-ge'ar train 'in a predetermined position'of rest.

2. The normalizing device for camera shutter retards defined in claim 1 characterized inthat the gear train is moved-by a springtowards a rest position after exposure and in that' the perm'anent magnet may-influence movement of the n V I a g polarized member during movement of the gear 75 6. Anormalizingfievice'forcamerashuttergear train under the influence ofits spring towards its rest position; thereby orientingthefigears of the geartrainas'they approach a restpQSitiOn.

'- 3. Ano'rmalizing device for camera-shutters 'of the type" including a shutter- 'casinggan exposure aperture therein; shutterf leaves pivotallyi'rnoved in the shutter and normally covering the-exposure aperture; a -power-driven masterniember operably connected to the shutter blades for movingthe blades to open and" close the exposure aperture; a latchfor themaster member, a'l'atchreleasingmechanism including a trigger; retard comprising atrain of gears one of which a C ntact sector adapted to be driven by theniaster member'to control the speed of operation thereof,

i means tocontrol the shutter speed by moving the contact sector relative'to the master member,

said normalizing'device comprising the geartrain and means tending to maintain the'contact gear and a starwheel in a predetermined relationship 7 to each other, said means comprising a polarized member included With the sta rwheel" and apermanent magnet adjacent the "path" of the polar- "ized member'to exert a" force thereontending' to turn the starwheel to a predetermined position With respect to the contact gear. 7 I I l. A normalizingdevice for camera shutters of the type including a shutter "casing; an exposure aperture therein; shutter leaves 'pivotally moved in the shutter and normally covering the""expo sure aperture; a power-driven master member operably connected to the shutter blades for moving the blades to openand closethe exposure aperture; a'latch for the'master member; a latchreleasing mechanism including a trigger; a-fetard comprising a train of'gears'one' of 'whiclf'is a contact sector adapted to be-drivenby the'mas-' ter member to control the vspeed of operation thereof. means to control the shutter speedby moving the contact sector relative to the master member, said normalizing device comprising the -gear train and means for orienting a star-"wheel atone end of the gear trainwith the-orientation 1 of the contact sector at the'other end there'of,

. said orienting means comprising-polarized material on the starwheel and a permanent magnet carried adjacent the periphery ofthe starvvheel periphery andfixedly mounted on the-shutter,

and a spring normally turning-the contact sector toward a normal position of rest.

5. A normalizing device for photographicshutters, retards for shutters of-the type employing a shutter casing having an exposureaperture; a pivotally mounted shutter leaf mounted-to 'move to and from an aperture-covering position} a.

1 master member operably connected to thesliutter leaf, a trigger-for engaging andreleasin'gthe master member; said retard comprising a: gear train one element of which'is'positionabl'e inthe path of the master member-to delay thei-operation thereof, said gear train including Wheels 1 adapted to turn on shafts-at progressively greater speeds from one end to the other, a normalizing "device comprising a pieceof polarized? material aflixed to the fastest moving gear I train" Wheel and extending atright' angles tothe shaft thereof,

1 and a permanent magnet positioned adjacent to, but'out of,'alignment with' the axis o'f'the'polariz'ed material 'vvhereby said magnet may always retardwhenone element there'of is 'strucl' by the master-member.

retards for shutters of the type including a shutter casing having an exposure aperture therein, a trigger for releasing the shutter, shutter leaves for opening and closing the exposure aperture, mechanism for operating the shutter leaves to open and close the aperture and including a pin moving through a path when the leaves are moving, said gear train comprising a sector having an adjustably mounted arm and a train of gears, one moving faster than the other gears, means for positioning said arm to and from the path of movement of the pin for retarding movement of the arm, said normalizing device comprising two parts, a polarized member and a permanent magnet, one part mounted on the fastest moving gear of the gear train and the other part mounted on the shutter adjacent the path of the first-mentioned part, one part being oriented with respect to the other part to turn one part relative to the other part to orient the gears of the gear train relative to the sector thereof at a predetermined speed setting.

'7. A normalizing device for camera shutter retards for shutters of the type including a shutter casing having an exposure aperture therein, blades pivotally mounted therein, shutter mechanism operably connected to the shutter blades for moving the blades to open and close the aperture, said mechanism including a trigger and a protuberance moving through a path, a speed setting dial, a gear retard having an arm movable by the speed setting dial to and from the path of the protuberance, said gear retard including a gear moving faster than the other gears and moving more than one revolution for all exposures except a fast exposure for which said fast gear moves less than one revolution, said normalizing device comprising a coacting magnet and a polarized member, one carried by the fast gear and the other by the shutter and oriented relatively to each other for turning the fast gear in one direction and into a position of rest when said shutter is set for a fast exposure during which said fast gear moves less than one revolution, whereby the coacting magnet and polarized member may retain a predetermined relationship between the fast gears of the gear train and the arm.

8. A shutter comprising, in combination, a shutter casing, an exposure aperture therein, shutter leaves pivotally mounted in the shutter and normally covering the exposure aperture, a power drive having a protuberance and operably connected to the shutter blades for moving the blades for opening and closing the exposure aperture, a latch on the power drive, a latch-releasing mechanism including a trigger, a retard comprising a gear train, one element of which is a contact sector adapted to lie in the path of the protuberance to be driven thereby to control the speed of operation thereof, means to set the shutter speed including moving the contact sector relative to the power drive, and a retard normalizing device comprising a polarized member supported by a member of the gear train spaced from the contact gear sector and a permanent magnet adjacent thereto whereby the magnet and polarized member may regulate the position of gears of the gear train relative to the contact sector.

HOWARD T. HODGES.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,410,649 Fuerst Nov. 5, 1946 2,494,042 Fuerst Jan. 10, 1950 

